guys, I think you all got this very wrong: coppermine can manage files, videos and sorts of other document types, but after all it doesn't display none of them - jpeg, gif, png or swf files are displayed by your browser (because your browser is capable of doing this). When using movies files like wmv, avi or similar, all that coppermine does is keeping track of the location of those files, and send the files to the client PC. Coppermine then tells the client PC that it's a movie file and it should embedd the player (that has to be installed on the client PC) directly into the page in the browser if possible. If you use a pdf with coppermine, then an app like Adobe's Acrobat or similar needs to exist on the client if the user is meant to actually see it.
The very same thing goes for other file types like your 3gp files: Coppermine itself doesn't provide a player to the client that can display the movie, but the player has to exist on the client. You (as owner of a cell phone that comes with a CD containing a sync app and maybe even a software 3gp player) can play files named "foobar.3gp", while most users who don't have such an app installed won't be able to display such files no matter what.
Coppermine out-of-the-box is configured to be used with files that:
- are so common that nearly everybody has got an app on his client PC that is capable to display that particular filetype
- is not executable in itself (unlike .exe or .vbs files)
All that the above mentioned plugin does is that it allows you to add filetypes to this pre-defined list of accepted files. However, it doesn't add the capability to a client PC to actually "play" that kind of files - simply because it can't; Coppermine doesn't install software on client PCs - it's a web app, nothing else.
If you want to enable your users to display/download 3gp files, then use the plugin and add 3gp to list of files accepted by coppermine, however you have to understand that they will only be able to display those files if they have installed a player for that particular file type on their client.